The present invention relates to a unit cell for a solid oxide fuel cell having a solid electrolyte to obtain electrical energy through electrochemical reaction and its related method and, more particularly, to a unit cell for a solid oxide fuel cell in which a solid electrolyte is sandwiched by electrodes and its manufacturing method.
In recent years, fuel cells have been attracting public attention as a clean energy source that is friendly to a global environmental concern. Among a variety of fuel cells, a solid oxide fuel cell (SOFC) is a fuel cell of the type in which, as an electrolyte, use is made of an oxide ion conductive solid electrolyte such as yttria stabilized zirconia to allow both surfaces (front and rear surfaces) thereof to be mounted with porous electrodes, and the solid electrolyte serves as a partition wall to permit fuel gas such as hydrogen and hydrocarbon to be supplied to one of the electrodes and to permit air or oxygen gas to be supplied to the remaining one of the electrodes to generally operate at the temperature of approximately 1000° C.
As a unit cell that forms such an SOFC, Japanese Patent Application Laid-Open Publication No. H4-92369 discloses a fuel cell wherein a fuel electrode, a ceria series electrolyte with a film thickness below 20 μm and a porous oxygen electrode are formed on an inorganic porous substrate to allow the inorganic porous substrate to serve as a current collector and a fuel gas passage while permitting the porous oxygen electrode to serve as an oxidizing gas passage. In the fuel cell, films of the fuel electrode, the electrolyte and the oxygen electrode are formed by PVD, CVD and plating methods and, further, a surface of the fuel electrode is once coated with organic material on which the electrolyte is formed on which, also, the oxygen electrode is formed whereupon the organic material is removed.
Further, a DLR cell which adopts a cell structure employing a porous metallic substrate as a support member for a fuel electrode, an electrolyte and an air electrode is known (Plasma Sprayed Thin-Film SOFC for Reduced Operating Temperature, Fuel Cells Bulletin, pp597 –600, 2000). In this literature, films of the fuel electrode, the electrolyte and the air electrode are formed on the porous metallic substrate by a spraying method.